A) Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing a semiconductor device, and, more particularly, to a semiconductor device having an insulation film of a high dielectric constant and a method of manufacturing the semiconductor device.
B) Description of the Related Art
Insulated gate (IG) field effect transistors (FETs), typical examples of which are MOS transistors, are widely used as typical semiconductor devices used in a semiconductor integrated circuit device. For a larger scale integration of semiconductor integrated circuit devices, IG-FETs have been miniaturized according the scaling law. Miniaturization can reduce the sizes of IG-FETs, such as making the gate insulation film thinner and shortening the gate length, and improve the performances of miniaturized devices while keeping the normal performances.
The gate insulation films of MOS transistors of the next generation should be made as thin as 2 nm or less. With that film thickness, the tunnel current starts flowing, the gate leak current becomes uncontrollable, and an increase in power dissipation cannot be avoided. To suppress the tunnel current which flows through the gate insulation film, the gate insulation film in use should be thick.
To increase the physical thickness of the gate insulation film while keeping the effective thickness of the gate insulation film equivalent to a silicon oxide film, the use of a high-dielectric-constant insulation material having a specific dielectric constant higher than that of a silicon oxide for the gate insulation film has been proposed. The specific dielectric constant of the silicon oxide is said to be, for example, approximately 3.5 to 4.5, depending on the deposition method. The specific dielectric constant of a silicon nitride is higher than that of the silicon oxide, and is said to be approximately 7 to 8.
Japanese Patent Laid-Open Publication No. 2001-274378 proposes the use of barium titanate (Ba(Sr)TiO3), titanium oxide (TiO2), tantalum oxide (Ta2O5), zirconium oxide (ZrO2), hafnium oxide (HfO2), silicon nitride (Si3N4), or alumina (Al2O3), which has a specific dielectric constant higher than that of silicon oxide, for a gate insulation film. The publication also proposes a structure where a silicon oxide film is intervened between such a high-dielectric-constant insulation film and a silicon substrate.
The use of a new material having a high specific dielectric constant for the gate insulation film of an IG-FET brings about a new problem. Solving such a new problem is desired to promote the practical use of new materials.